CHICAGO, Nov. 22 -- Sen. Barack Obama said President Bush should admit mistakes in waging the Iraq war and reduce the number of troops stationed there in the next year. But the Illinois Democrat, a longtime opponent of the war, said U.S. forces remain part of a solution in the bitterly divided country and should not be withdrawn immediately.

Without citing specific numbers, Obama called for a limited drawdown of U.S. troops that would push the fragile Iraqi government to take more responsibility while deploying enough American soldiers to prevent the country from exploding into civil war or ethnic cleansing or a haven for terrorism.

Sen. Barack Obama (D-Ill.) greets well-wishers at the Chicago Council on Foreign Relations after he said the administration has not given straight answers to critical questions on Iraq. (By Jeff Roberson -- Associated Press)

Obama also faulted the administration for tarring its critics as unpatriotic naysayers and said it launched the war to topple Saddam Hussein in March 2003 without giving either Congress or the American people the full story.

Straight answers to critical questions. That's what we don't have right now, the high-profile freshman senator told the Chicago Council on Foreign Relations. Members of both parties and the American people have now made clear that it is simply not enough for the president to simply say 'We know best' and 'Stay the course.'

As other Democrats are finding their voice against Iraq policy, Obama took an approach closer to one taken by Senate Foreign Relations Committee colleague Joseph R. Biden Jr. (D-Del.) than to that of Rep. John P. Murtha (D-Pa.). Murtha, a former Marine, called last week for an immediate pullout of nearly 160,000 U.S. troops.

Four prospective Democratic presidential candidates -- Biden, Sen. Hillary Rodham Clinton (N.Y.), Sen. John F. Kerry (Mass.) and former North Carolina senator John Edwards -- have advocated a more gradual approach, with no sudden steps. Biden called Monday for the withdrawal of 50,000 troops by the end of next year and all but 20,000 to 40,000 out by January 2008.

Obama told the audience of about 500 people that the war has siphoned assets from homeland security and the global anti-terrorism fight. He said the administration's attempt to equate the defeat of the Iraqi insurgency with the defeat of international terrorism is overly narrow and dangerously short-sighted.

In a 35-minute speech scheduled just days ago, Obama argued that public opinion has raced ahead of politicians in seeking a clearly etched policy that helps produce stability in Iraq and the Middle East without exposing the United States to a war without end -- a war where our goals and our strategies drift aimlessly, regardless of the cost in lives or dollars spent.

Those of us in Washington have fallen behind the debate that is taking place across America on Iraq. We are failing to provide leadership on this issue, Obama said.

He maintained that Bush could take politics out of the Iraq discussion once and for all if he would simply go on television and say to the American people: 'Yes, we made mistakes. Yes, there are things I would have done differently. But now that I'm here, I'm willing to work with both Republicans and Democrats to find the most responsible way out.'